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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2009 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.util.concurrent;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import static com.google.common.base.Preconditions.checkNotNull;<a name="line.19"></a>
<span class="sourceLineNo">020</span><a name="line.20"></a>
<span class="sourceLineNo">021</span>import com.google.common.annotations.Beta;<a name="line.21"></a>
<span class="sourceLineNo">022</span><a name="line.22"></a>
<span class="sourceLineNo">023</span>import java.util.concurrent.Executor;<a name="line.23"></a>
<span class="sourceLineNo">024</span>import java.util.concurrent.Executors;<a name="line.24"></a>
<span class="sourceLineNo">025</span>import java.util.concurrent.Future;<a name="line.25"></a>
<span class="sourceLineNo">026</span>import java.util.concurrent.ThreadFactory;<a name="line.26"></a>
<span class="sourceLineNo">027</span>import java.util.concurrent.atomic.AtomicBoolean;<a name="line.27"></a>
<span class="sourceLineNo">028</span><a name="line.28"></a>
<span class="sourceLineNo">029</span>/**<a name="line.29"></a>
<span class="sourceLineNo">030</span> * Utilities necessary for working with libraries that supply plain {@link<a name="line.30"></a>
<span class="sourceLineNo">031</span> * Future} instances. Note that, whenver possible, it is strongly preferred to<a name="line.31"></a>
<span class="sourceLineNo">032</span> * modify those libraries to return {@code ListenableFuture} directly.<a name="line.32"></a>
<span class="sourceLineNo">033</span> *<a name="line.33"></a>
<span class="sourceLineNo">034</span> * @author Sven Mawson<a name="line.34"></a>
<span class="sourceLineNo">035</span> * @since 10.0 (replacing {@code Futures.makeListenable}, which<a name="line.35"></a>
<span class="sourceLineNo">036</span> *     existed in 1.0)<a name="line.36"></a>
<span class="sourceLineNo">037</span> */<a name="line.37"></a>
<span class="sourceLineNo">038</span>@Beta<a name="line.38"></a>
<span class="sourceLineNo">039</span>public final class JdkFutureAdapters {<a name="line.39"></a>
<span class="sourceLineNo">040</span>  /**<a name="line.40"></a>
<span class="sourceLineNo">041</span>   * Assigns a thread to the given {@link Future} to provide {@link<a name="line.41"></a>
<span class="sourceLineNo">042</span>   * ListenableFuture} functionality.<a name="line.42"></a>
<span class="sourceLineNo">043</span>   *<a name="line.43"></a>
<span class="sourceLineNo">044</span>   * &lt;p&gt;&lt;b&gt;Warning:&lt;/b&gt; If the input future does not already implement {@code<a name="line.44"></a>
<span class="sourceLineNo">045</span>   * ListenableFuture}, the returned future will emulate {@link<a name="line.45"></a>
<span class="sourceLineNo">046</span>   * ListenableFuture#addListener} by taking a thread from an internal,<a name="line.46"></a>
<span class="sourceLineNo">047</span>   * unbounded pool at the first call to {@code addListener} and holding it<a name="line.47"></a>
<span class="sourceLineNo">048</span>   * until the future is {@linkplain Future#isDone() done}.<a name="line.48"></a>
<span class="sourceLineNo">049</span>   *<a name="line.49"></a>
<span class="sourceLineNo">050</span>   * &lt;p&gt;Prefer to create {@code ListenableFuture} instances with {@link<a name="line.50"></a>
<span class="sourceLineNo">051</span>   * SettableFuture}, {@link MoreExecutors#listeningDecorator(<a name="line.51"></a>
<span class="sourceLineNo">052</span>   * java.util.concurrent.ExecutorService)}, {@link ListenableFutureTask},<a name="line.52"></a>
<span class="sourceLineNo">053</span>   * {@link AbstractFuture}, and other utilities over creating plain {@code<a name="line.53"></a>
<span class="sourceLineNo">054</span>   * Future} instances to be upgraded to {@code ListenableFuture} after the<a name="line.54"></a>
<span class="sourceLineNo">055</span>   * fact.<a name="line.55"></a>
<span class="sourceLineNo">056</span>   */<a name="line.56"></a>
<span class="sourceLineNo">057</span>  public static &lt;V&gt; ListenableFuture&lt;V&gt; listenInPoolThread(<a name="line.57"></a>
<span class="sourceLineNo">058</span>      Future&lt;V&gt; future) {<a name="line.58"></a>
<span class="sourceLineNo">059</span>    if (future instanceof ListenableFuture) {<a name="line.59"></a>
<span class="sourceLineNo">060</span>      return (ListenableFuture&lt;V&gt;) future;<a name="line.60"></a>
<span class="sourceLineNo">061</span>    }<a name="line.61"></a>
<span class="sourceLineNo">062</span>    return new ListenableFutureAdapter&lt;V&gt;(future);<a name="line.62"></a>
<span class="sourceLineNo">063</span>  }<a name="line.63"></a>
<span class="sourceLineNo">064</span><a name="line.64"></a>
<span class="sourceLineNo">065</span>  /**<a name="line.65"></a>
<span class="sourceLineNo">066</span>   * Submits a blocking task for the given {@link Future} to provide {@link<a name="line.66"></a>
<span class="sourceLineNo">067</span>   * ListenableFuture} functionality.<a name="line.67"></a>
<span class="sourceLineNo">068</span>   *<a name="line.68"></a>
<span class="sourceLineNo">069</span>   * &lt;p&gt;&lt;b&gt;Warning:&lt;/b&gt; If the input future does not already implement {@code<a name="line.69"></a>
<span class="sourceLineNo">070</span>   * ListenableFuture}, the returned future will emulate {@link<a name="line.70"></a>
<span class="sourceLineNo">071</span>   * ListenableFuture#addListener} by submitting a task to the given executor at<a name="line.71"></a>
<span class="sourceLineNo">072</span>   * at the first call to {@code addListener}. The task must be started by the<a name="line.72"></a>
<span class="sourceLineNo">073</span>   * executor promptly, or else the returned {@code ListenableFuture} may fail<a name="line.73"></a>
<span class="sourceLineNo">074</span>   * to work.  The task's execution consists of blocking until the input future<a name="line.74"></a>
<span class="sourceLineNo">075</span>   * is {@linkplain Future#isDone() done}, so each call to this method may<a name="line.75"></a>
<span class="sourceLineNo">076</span>   * claim and hold a thread for an arbitrary length of time. Use of bounded<a name="line.76"></a>
<span class="sourceLineNo">077</span>   * executors or other executors that may fail to execute a task promptly may<a name="line.77"></a>
<span class="sourceLineNo">078</span>   * result in deadlocks.<a name="line.78"></a>
<span class="sourceLineNo">079</span>   *<a name="line.79"></a>
<span class="sourceLineNo">080</span>   * &lt;p&gt;Prefer to create {@code ListenableFuture} instances with {@link<a name="line.80"></a>
<span class="sourceLineNo">081</span>   * SettableFuture}, {@link MoreExecutors#listeningDecorator(<a name="line.81"></a>
<span class="sourceLineNo">082</span>   * java.util.concurrent.ExecutorService)}, {@link ListenableFutureTask},<a name="line.82"></a>
<span class="sourceLineNo">083</span>   * {@link AbstractFuture}, and other utilities over creating plain {@code<a name="line.83"></a>
<span class="sourceLineNo">084</span>   * Future} instances to be upgraded to {@code ListenableFuture} after the<a name="line.84"></a>
<span class="sourceLineNo">085</span>   * fact.<a name="line.85"></a>
<span class="sourceLineNo">086</span>   *<a name="line.86"></a>
<span class="sourceLineNo">087</span>   * @since 12.0<a name="line.87"></a>
<span class="sourceLineNo">088</span>   */<a name="line.88"></a>
<span class="sourceLineNo">089</span>  public static &lt;V&gt; ListenableFuture&lt;V&gt; listenInPoolThread(<a name="line.89"></a>
<span class="sourceLineNo">090</span>      Future&lt;V&gt; future, Executor executor) {<a name="line.90"></a>
<span class="sourceLineNo">091</span>    checkNotNull(executor);<a name="line.91"></a>
<span class="sourceLineNo">092</span>    if (future instanceof ListenableFuture) {<a name="line.92"></a>
<span class="sourceLineNo">093</span>      return (ListenableFuture&lt;V&gt;) future;<a name="line.93"></a>
<span class="sourceLineNo">094</span>    }<a name="line.94"></a>
<span class="sourceLineNo">095</span>    return new ListenableFutureAdapter&lt;V&gt;(future, executor);<a name="line.95"></a>
<span class="sourceLineNo">096</span>  }<a name="line.96"></a>
<span class="sourceLineNo">097</span><a name="line.97"></a>
<span class="sourceLineNo">098</span>  /**<a name="line.98"></a>
<span class="sourceLineNo">099</span>   * An adapter to turn a {@link Future} into a {@link ListenableFuture}.  This<a name="line.99"></a>
<span class="sourceLineNo">100</span>   * will wait on the future to finish, and when it completes, run the<a name="line.100"></a>
<span class="sourceLineNo">101</span>   * listeners.  This implementation will wait on the source future<a name="line.101"></a>
<span class="sourceLineNo">102</span>   * indefinitely, so if the source future never completes, the adapter will<a name="line.102"></a>
<span class="sourceLineNo">103</span>   * never complete either.<a name="line.103"></a>
<span class="sourceLineNo">104</span>   *<a name="line.104"></a>
<span class="sourceLineNo">105</span>   * &lt;p&gt;If the delegate future is interrupted or throws an unexpected unchecked<a name="line.105"></a>
<span class="sourceLineNo">106</span>   * exception, the listeners will not be invoked.<a name="line.106"></a>
<span class="sourceLineNo">107</span>   */<a name="line.107"></a>
<span class="sourceLineNo">108</span>  private static class ListenableFutureAdapter&lt;V&gt; extends ForwardingFuture&lt;V&gt;<a name="line.108"></a>
<span class="sourceLineNo">109</span>      implements ListenableFuture&lt;V&gt; {<a name="line.109"></a>
<span class="sourceLineNo">110</span><a name="line.110"></a>
<span class="sourceLineNo">111</span>    private static final ThreadFactory threadFactory =<a name="line.111"></a>
<span class="sourceLineNo">112</span>        new ThreadFactoryBuilder()<a name="line.112"></a>
<span class="sourceLineNo">113</span>            .setDaemon(true)<a name="line.113"></a>
<span class="sourceLineNo">114</span>            .setNameFormat("ListenableFutureAdapter-thread-%d")<a name="line.114"></a>
<span class="sourceLineNo">115</span>            .build();<a name="line.115"></a>
<span class="sourceLineNo">116</span>    private static final Executor defaultAdapterExecutor =<a name="line.116"></a>
<span class="sourceLineNo">117</span>        Executors.newCachedThreadPool(threadFactory);<a name="line.117"></a>
<span class="sourceLineNo">118</span><a name="line.118"></a>
<span class="sourceLineNo">119</span>    private final Executor adapterExecutor;<a name="line.119"></a>
<span class="sourceLineNo">120</span><a name="line.120"></a>
<span class="sourceLineNo">121</span>    // The execution list to hold our listeners.<a name="line.121"></a>
<span class="sourceLineNo">122</span>    private final ExecutionList executionList = new ExecutionList();<a name="line.122"></a>
<span class="sourceLineNo">123</span><a name="line.123"></a>
<span class="sourceLineNo">124</span>    // This allows us to only start up a thread waiting on the delegate future<a name="line.124"></a>
<span class="sourceLineNo">125</span>    // when the first listener is added.<a name="line.125"></a>
<span class="sourceLineNo">126</span>    private final AtomicBoolean hasListeners = new AtomicBoolean(false);<a name="line.126"></a>
<span class="sourceLineNo">127</span><a name="line.127"></a>
<span class="sourceLineNo">128</span>    // The delegate future.<a name="line.128"></a>
<span class="sourceLineNo">129</span>    private final Future&lt;V&gt; delegate;<a name="line.129"></a>
<span class="sourceLineNo">130</span><a name="line.130"></a>
<span class="sourceLineNo">131</span>    ListenableFutureAdapter(Future&lt;V&gt; delegate) {<a name="line.131"></a>
<span class="sourceLineNo">132</span>      this(delegate, defaultAdapterExecutor);<a name="line.132"></a>
<span class="sourceLineNo">133</span>    }<a name="line.133"></a>
<span class="sourceLineNo">134</span><a name="line.134"></a>
<span class="sourceLineNo">135</span>    ListenableFutureAdapter(Future&lt;V&gt; delegate, Executor adapterExecutor) {<a name="line.135"></a>
<span class="sourceLineNo">136</span>      this.delegate = checkNotNull(delegate);<a name="line.136"></a>
<span class="sourceLineNo">137</span>      this.adapterExecutor = checkNotNull(adapterExecutor);<a name="line.137"></a>
<span class="sourceLineNo">138</span>    }<a name="line.138"></a>
<span class="sourceLineNo">139</span><a name="line.139"></a>
<span class="sourceLineNo">140</span>    @Override<a name="line.140"></a>
<span class="sourceLineNo">141</span>    protected Future&lt;V&gt; delegate() {<a name="line.141"></a>
<span class="sourceLineNo">142</span>      return delegate;<a name="line.142"></a>
<span class="sourceLineNo">143</span>    }<a name="line.143"></a>
<span class="sourceLineNo">144</span><a name="line.144"></a>
<span class="sourceLineNo">145</span>    @Override<a name="line.145"></a>
<span class="sourceLineNo">146</span>    public void addListener(Runnable listener, Executor exec) {<a name="line.146"></a>
<span class="sourceLineNo">147</span>      executionList.add(listener, exec);<a name="line.147"></a>
<span class="sourceLineNo">148</span><a name="line.148"></a>
<span class="sourceLineNo">149</span>      // When a listener is first added, we run a task that will wait for<a name="line.149"></a>
<span class="sourceLineNo">150</span>      // the delegate to finish, and when it is done will run the listeners.<a name="line.150"></a>
<span class="sourceLineNo">151</span>      if (hasListeners.compareAndSet(false, true)) {<a name="line.151"></a>
<span class="sourceLineNo">152</span>        if (delegate.isDone()) {<a name="line.152"></a>
<span class="sourceLineNo">153</span>          // If the delegate is already done, run the execution list<a name="line.153"></a>
<span class="sourceLineNo">154</span>          // immediately on the current thread.<a name="line.154"></a>
<span class="sourceLineNo">155</span>          executionList.execute();<a name="line.155"></a>
<span class="sourceLineNo">156</span>          return;<a name="line.156"></a>
<span class="sourceLineNo">157</span>        }<a name="line.157"></a>
<span class="sourceLineNo">158</span><a name="line.158"></a>
<span class="sourceLineNo">159</span>        adapterExecutor.execute(new Runnable() {<a name="line.159"></a>
<span class="sourceLineNo">160</span>          @Override<a name="line.160"></a>
<span class="sourceLineNo">161</span>          public void run() {<a name="line.161"></a>
<span class="sourceLineNo">162</span>            try {<a name="line.162"></a>
<span class="sourceLineNo">163</span>              delegate.get();<a name="line.163"></a>
<span class="sourceLineNo">164</span>            } catch (Error e) {<a name="line.164"></a>
<span class="sourceLineNo">165</span>              throw e;<a name="line.165"></a>
<span class="sourceLineNo">166</span>            } catch (InterruptedException e) {<a name="line.166"></a>
<span class="sourceLineNo">167</span>              Thread.currentThread().interrupt();<a name="line.167"></a>
<span class="sourceLineNo">168</span>              // Threads from our private pool are never interrupted.<a name="line.168"></a>
<span class="sourceLineNo">169</span>              throw new AssertionError(e);<a name="line.169"></a>
<span class="sourceLineNo">170</span>            } catch (Throwable e) {<a name="line.170"></a>
<span class="sourceLineNo">171</span>              // ExecutionException / CancellationException / RuntimeException<a name="line.171"></a>
<span class="sourceLineNo">172</span>              // The task is done, run the listeners.<a name="line.172"></a>
<span class="sourceLineNo">173</span>            }<a name="line.173"></a>
<span class="sourceLineNo">174</span>            executionList.execute();<a name="line.174"></a>
<span class="sourceLineNo">175</span>          }<a name="line.175"></a>
<span class="sourceLineNo">176</span>        });<a name="line.176"></a>
<span class="sourceLineNo">177</span>      }<a name="line.177"></a>
<span class="sourceLineNo">178</span>    }<a name="line.178"></a>
<span class="sourceLineNo">179</span>  }<a name="line.179"></a>
<span class="sourceLineNo">180</span><a name="line.180"></a>
<span class="sourceLineNo">181</span>  private JdkFutureAdapters() {}<a name="line.181"></a>
<span class="sourceLineNo">182</span>}<a name="line.182"></a>




























































</pre>
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